Question

what are alkyl halides? How are they classified?

Answer 1

Hint: Long chain carbon and hydrogen compounds or hydrocarbons are called as alkyl groups. The group 17 elements are termed as halogens. The anions of halogens are termed as halides that are $C{{l}^{-}},B{{r}^{-}}$etc. These are also termed as functional groups that can be substituted into hydrocarbons. They are called halo functional groups.

Complete answer:
When a hydrocarbon chain made up of alkyl groups has a halo atom substituted after the removal of one hydrogen atom, then alkyl halides are formed. These can also be termed as halo alkanes. An alkyl halide basically contains a halogen atom attached with the carbon atom that is $s{{p}^{3}}$ hybridized. Examples of alkyl halides are ethyl chloride $C{{H}_{3}}C{{H}_{2}}Cl$, propyl bromide $C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}Br$ etc.
Alkyl halides can be classified into three main groups as primary$\left( 1{}^\circ \right)$, secondary $\left( 2{}^\circ \right)$, and tertiary $\left( 3{}^\circ \right)$alkyl halides.
-Primary or $\left( 1{}^\circ \right)$alkyl halides consist of the halogen atom attached with that carbon that is attached with only one adjacent carbon atom, example ethyl chloride $C{{H}_{3}}C{{H}_{2}}Cl$.
-Secondary or $\left( 2{}^\circ \right)$ alkyl halides consist of the halogen atom attached with that carbon that is attached with two other carbon atoms, example isopropyl chloride $C{{H}_{3}}CH(Cl)C{{H}_{3}}$
-Tertiary or $\left( 3{}^\circ \right)$ alkyl halides consist of the halogen atom attached with that carbon that is attached with three other carbon atoms, example tert butyl chloride ${{\left( C{{H}_{3}} \right)}_{3}}CCl$
Hence, alkyl halides are alkanes having a halo atom as a functional group. They are classified into primary $\left( 1{}^\circ \right)$, secondary$\left( 2{}^\circ \right)$, and tertiary $\left( 3{}^\circ \right)$alkyl halides.

Note:
On the basis of the number of halogen atoms the haloalkanes are classified as monohalogen, dihalogen and trihalogen derivatives having 1, 2 and 3 halogen atoms respectively. Also, some other types of haloalkanes are allylic halides in which the halo atom is attached with a carbon atom attached next to a double bond and benzylic halides having a benzene group.